1. Technical Field
The present invention relates to a damper for controlling the flow of air through a passage and more particularly relates to an temperature responsive, automatic damper particularly useful with a wind-powered, roof-mounted turbine attic ventilator, the damper having means for controlling air flow through the damper when the damper is in an otherwise xe2x80x9cclosedxe2x80x9d position.
2. Background of the Invention
Most confined spaces such as the attic of a house, building, etc. must be ventilated during the warmer periods of the year in order to prevent excessive heat buildup therein. That is, the attic of a house, if unventilated, can reach extremely high temperatures during the summer months in most areas. This retained heat normally results in substantially higher costs for cooling the building and can lead to other maintenance problems. While there are various means for ventilating these spaces, probably the most common and widely used is the roof mounted, wind-powered turbine ventilator, especially in warmer climates.
In a typical installation, the wind turbine is mounted onto a conduit which, in turn, is fixed over an opening cut through the roof of the structure. The wind causes the turbine blades to rotate which creates a suction which, in turn, draws air from the space below the roof (e.g. hereinafter referred to as xe2x80x9catticxe2x80x9d), through the conduit, and out through the spinning turbine.
Such turbines are highly effective in exhausting hot air from attics during the hot periods of the year. Unfortunately, these turbines also continue to remove relatively warm air from the attic during colder periods which, in turn, is replaced with frigid, ambient entering the attic through the structure""s under eave sofit vents. As easily recognized, this is not good since the temperature in the attic can drop to extremely low levels which, in turn, can adversely affect the desired heating of the structure during these cold periods. That is, if the temperature in the attic becomes too cold, the heating system in the structure may not be able to adequately heat the structure and, at the very least, can lead to substantially higher energy usage and heating costs. Accordingly, it has long been recognized that it is desirable to block airflow through these turbines during the colder months of the year.
There are several known techniques for controlling the airflow through roof-mounted turbines during high and low temperature cycles. Probably the simplest way to conserve attic heat in the winter is by externally securing a cover (e.g. plastic trash bag) over the turbine during the colder periods, thus stopping airflow through the turbine. Such deployed plastic bags are unsightly and require the installer to crawl onto the roof which can be dangerous.
Another technique is to manually force a xe2x80x9cplunger-likexe2x80x9d compressible stopper into the ventilation conduit to block substantially all of the air flow through the ventilation conduit during colder periods. This technique is unreliable and inconvenient since it require a person to physically crawl through the attic at the appropriate times of the year to place and remove the stopper from the ventilation conduit.
A more sophisticated, known technique involves positioning an xe2x80x9cautomaticxe2x80x9d damper in the ventilation conduit between the turbine and the opening through the roof. These dampers are designed to move between (a) a fully xe2x80x9copenxe2x80x9d position when the ambient temperature rises above a set value (e.g. 80xc2x0 F.) to allow maximum air flow through the turbine and (b) a fully xe2x80x9cclosedxe2x80x9d position when the temperature drops below the set value to block substantially all air flow through the ventilation conduit.
Most known, prior art automatic dampers of the type used with roof-mounted turbine ventilators have two or more vanes or louvers that are pivotably mounted in a housing. The louvers are moved between their open and closed positions by a means (e.g. a bimetal element such as a coil, spring, etc.) which, in turn, is responsive to the ambient temperature. For examples of such known dampers, see U.S. Pat. Nos. 3,976,245; 4,123,001; 4,372,485; 4,582,250; 4,697,736; and 4,919,329.
While some of these types of automatic dampers have achieved varying degrees of commercial success, it is considered that there are certain disadvantages associated therewith. A major disadvantage is that dampers of this type normally have only a fully open position which allows maximum air flow during hotter periods and a fully closed position which substantially blocks all of the air flow during colder periods. While such dampers may be ideal when considering only the heating and cooling of a structure, other concerns relating to confined spaces such as attics have arisen which make the use of such dampers less attractive.
That is, in a totally closed, non-ventilated attic, moisture is likely to collect during the colder months which, in turn, can readily provide a xe2x80x9cbreeding groundxe2x80x9d for xe2x80x9cblack moldxe2x80x9d and like growths. As has been well advertised, the presence of black mold in residences and other structures has become a serious problem creating hazardous health conditions and requiring thousands of dollars to rectify. In fact, the problem of mold recently has grown to such an extent that many insurance companies no longer offer coverage in many areas.
Another disadvantage of these known dampers is that the dampers are not interchangeable between the particular ventilating conduits presently available from several different manufacturers. That is, even if it may be possible to retrofit a previously installed conduit with a damper, a specially designed damper for that respective conduit would be required. This prevents a supplier from stocking a single, universal damper that would be usable with most presently available ventilation conduits.
Further, due to the widths of the louvers of the known dampers, most, if not all, of these dampers can not be retrofitted into certain existing ventilation conduits such as those required for mounting a turbine onto highly pitched roofs. These limitations seriously affect the commercial exploitation of an automatic damper that can be easily and quickly installed into almost all-existing ventilation conduits as a retrofit by an unskilled craftsman.
Still further, previous automatic dampers that have been proposed for use with wind-powered, roof top ventilators have not lent themselves to low cost, fast assembly or mass production. Typically, they require several punched metal parts that are held together by many rivets, screws and nuts and most exhibit many metal-on-metal wearing surfaces. A typical, prior art damper has components that are prone to wear out easily and get out of adjustment causing it to have a very limited life. Additionally, most require a thick and expensive bimetal coil to lift their heavy metal louvers. Also, the mechanical action for moving the louvers of these dampers is somewhat complex and prone to an early failure.
The present invention provides a damper for controlling air flow through a passage wherein the damper is capable of allowing some degree of ventilation while, at the same time, blocking the majority of the air flow through the damper. The damper is especially useful in controlling air flow through ventilation conduits used to mount air turbines on the roof of a structure wherein the damper opens during warm periods of the year and then moves towards a closed position during colder periods. By allowing some xe2x80x9cwinter ventilationxe2x80x9d for attics and the like, the damper is beneficial in preventing an atmosphere within the attic which can support the growth of black mold, etc. but at the same time can block the majority of the air flow from the attic during the winter to thereby aid in retaining heat in the structure which, in turn, saves energy and the costs related thereto.
More specifically, the present invention provides a damper which has a means which selects a xe2x80x9cclosedxe2x80x9d position for the damper to allow a desired amount of air to flow therethrough (i.e. winter ventilation) when the damper is in this selected closed position. In a preferred embodiment, this means allows several different positions (e.g. between from about 0% to about 25% of maximum flow) to be selected depending on the needs and location of the user.
Basically, the present invention provides a low profile damper that is comprised of a housing having a plurality of louvers pivotably mounted therein. A linkage strip interconnects the louvers together so that all of the louvers move in unison between their open and closed positions. Preferably, the housing, louvers, linkage, and retainers for the louvers are molded from plastic whereby no metal fasteners and like with be required.
A temperature responsive element, e.g. bimetal coil, is directly connected between the housing and one of the louvers and moves the louvers to their open position when the ambient temperature heats up and moves the louvers toward their closed position when the weather cools.
In the preferred embodiment, the air flow selector means is comprised of a plurality of openings or a continuous slot which extend through the housing and are adapted to receive a detent which, in turn, will extend through the selected opening or the slot and into the arcuate path of at least one of the louvers. The positioning of the detent within a particular opening or at a particular point in the continuous slot will determine the degree of winter ventilation which is to be provided by the damper in that the louver will contact the detent as the louvers are being rotated towards their closed positions and will stop at the selected closed position of the damper.
It is recognized that while an universal, adjustable damper may be preferred by many since such a damper can be adjusted to the particular climate in which it is to be used. That is, where the temperature is xe2x80x9cwarmxe2x80x9d during the winter and the humidity and moisture content is high, the damper would most likely be set at its highest setting (e.g. 25% flow rate). Conversely, in extreme cold and/or dry climates, the damper is likely to be set at its minimum setting (about 0%).
However, where the winter climate is basically constant, year to year, a user may prefer a xe2x80x9cfactory presetxe2x80x9d damper which moves between a fully open position and a single selected closed position. In accordance with the present invention, the air flow selector means of one embodiment comprises gaps between adjacent louvers and/or openings or slots in one or more louvers which, when the louvers are in their selected closed position allow a predetermined amount of air to flow through the damper. In another embodiment, interference means, e.g. stops on at least one louver, are provided which block further rotation of the louvers when they reach their selected closed position.